While multiple methods of physical vapor deposition (PVD) exist, plasma sputtering and electron-beam evaporation are two of the most common. Knowing the difference between sputtering and evaporation can help you determine which option better suits your PVD application.
In sputtering, energetic ions collide with a target to detach or sputter atoms from the target material. Alternatively, evaporation involves heating the source material past its vaporization temperature.
As straightforward as this might sound, there’s much more to these PVD methods. This post compares the two methods, explaining what they are and highlighting their pros and cons.
Sputtering Explained
Sputtering is a PVD process that enables the creation of thin films using sputtered atoms. Sputter systems come in various types, including ion beam and magnetron sputtering.
Ion beam sputtering involves focusing an ion-electron beam on a target to sputter material onto a substrate.
The process begins by placing the surface that needs the coating inside a vacuum chamber filled with inert, non-reactive gas atoms.
The source material then receives a negative charge, which converts it into a cathode and causes free electrons to flow from it. The free electrons then collide with the electrons surrounding the negatively charged gas atoms.
As a result, the gas electrons are driven off, converting the gas atoms into positively charged, high-energy ions. The source material then attracts these ions, which collide at such high velocity that they detach atomic-sized particles.
The sputtered particles finally cross the chamber, landing on the substrate to create a film of ejected target ions.
Since the ions possess equal directionality and energy, this process helps achieve high film density and quality.
On the other hand, magnetron sputtering is a plasma-based coating method where positively charged ions from magnetically confined plasma collide with negatively charged source materials. The collision ejects atoms from the material, depositing them onto a substrate.
With the process occurring in a closed magnetic field, it traps electrons better, increasing efficiency. By doing so, the method helps produce good film quality and offers the highest scalability of any PVD method.
Thermal Evaporation Explained
The main difference between sputtering and evaporation is in how they create coating films.
You can read more about this PVD method in Korvus Technology’s detailed thermal evaporation article.
Thermal evaporation relies on heat to evaporate or sublimate a solid source material. However, similar to sputtering, thermal evaporation also comes in numerous forms, resistive thermal evaporation, and e-beam evaporation.
With resistive thermal evaporation, thermal energy is retrieved from a resistive heat source and applied to the solid-state source material in a vacuum chamber. The heat evaporates the material and creates high-pressure vapor, which condenses on a substrate and forms a thin film.
Due to the environment, the vacuum chamber creates, even low-pressure vapor can create a vapor cloud of evaporated particles that can stick to the substrate surface.
This evaporation method produces thicker coatings, permits fast flash evaporation, and works well for industrial applications that use electric contacts.
E-beam evaporation uses an electron beam, focusing a large amount of energy on the source material in a water-cooled crucible or copper hearth.
The electron beam creates extremely high temperatures that vaporize materials with high melting temperatures. This vapor then settles on a substrate, forming a film of the evaporated material.
Pros and Cons of Sputtering and Evaporation
Pros of Sputtering
Depending on which type of sputtering you opt for, you could enjoy several benefits. For instance, the advantages magnetron sputtering offers include:
- Uniformity, which helps you achieve a better yield
- Low impurity levels
- Impressive film density, with moderate to high stress
- Highest scalability rates, with automation available
- High deposition rate, ideal for applications with high throughput
Alternatively, with ion beam sputtering, you could enjoy perks such as:
- Excellent uniformity; the best of all PVD processes
- The lowest impurity levels of any PVD process
- Film of the highest quality, higher than all PVD processes
- Excellent and highly controlled directionality
- Ideal for low-temperature applications
- Lower scatter and absorption than other PVD processes
Cons of Sputtering
Yes, ion beam sputtering creates the densest, most high-quality films, and magnetron sputtering offers the highest scalability. However, these physical vapor deposition methods have a few downsides.
For instance, the drawbacks you could experience with magnetron sputtering include:
- Low directionality
- High costs
- High system complexity
- Poor deposition rates for dielectrics
- Substrate heating, especially when dealing with an energetic target material
Ion beam sputtering also has a few disadvantages, such as:
- High stress
- Low scalability, which reduces throughput
- Low deposition rates
- Highly complex and costly
- Slowest deposition method
Pros of Evaporation
As for evaporation, both e-beam and resistive thermal evaporation have distinct advantages and disadvantages.
For instance, e-beam evaporation offers benefits such as:
- Low impurity levels
- Good directionality
- High deposition rates
- High throughput
- Excellent uniformity when using masks and planetary
- Ion-assist source compatibility
Opting for resistive thermal evaporation allows you to enjoy the following:
- High deposition rates
- Simplicity
- Good directionality
- Affordability
- Excellent uniformity
The method is also ideal for materials with low melting points, can be used with non-metals and metals, and is suited for applications that use electrical contacts.
Cons of Evaporation
The drawbacks of resistive thermal evaporation include the following:
- Highest impurity levels
- Limited scalability
- Low-density film quality
- Moderate film stress
- Poor uniformity without masks and planetary
With e-beam evaporation, you’ll have to contend with:
- Moderate system complexity
- Moderate stress resistance
- Limited scalability at reduced deposition rates and utilization
- Moderate costs
Conclusion – Which Should You Use?
While sputtering produces better uniformity and film quality, it is more costly and complex. Alternatively, while evaporation is ideal for situations that require high throughput and volume production, it has limited scalability.
When deciding which method to use, pick the option that delivers the right balance of yield, cost, film quality, and throughput. You should also consider the method’s industrial application and your preferences.
Do you need help with your decision? Reach out to Korvus Technology.
We’d be happy to speak with you about the difference between sputtering and evaporation and how our HEX system can help.